1. Field
Example embodiments relate to a semiconductor laser device, a semiconductor laser device package and methods of manufacturing the same. Other example embodiments relate to a semiconductor laser device including a light shield plate, a semiconductor laser device package and methods of manufacturing the same.
2. Description of the Related Art
A laser, which mainly emits bluish purple light, may be manufactured using semiconductor material. Semiconductor laser devices may emit laser light from ultraviolet rays of a wavelength of about 360 nm to bluish green light of a wavelength of about 490 nm, and lasers in blue and purple regions of wavelengths of about 400 nm-about 450 nm may be used in various fields. Semiconductor laser devices having a wavelength of about 405 nm may be used as a light source of next-generation increased-capacity optical storage media, e.g., blu-ray disks (BD) and high-definition digital versatile disks (HD DVD). Semiconductor laser devices having a wavelength of about 450 nm may be used as a blue light source of laser display systems.
When semiconductor laser devices having wavelengths of about 500 nm or higher are available, the semiconductor laser devices may also be used as a green light source of laser display systems. Also, blue-purple semiconductor laser devices may be used as a light source of high-resolution laser printers. Semiconductor laser devices having relatively short wavelengths of about 400 nm or lower in the ultraviolet ray region may be manufactured using nitride semiconductor materials and applied for a biological or medical use. In nitride semiconductor laser devices, when an aluminum (Al) composition in the n-clad layer, which is formed of AIGaN, is not sufficiently high or when the n-clad layer is not sufficiently thick, the optical confinement may weaken, and thus, light may be leaked from a lower surface of the n-clad layer.
In nitride semiconductor laser devices employing a sapphire substrate, light leaked from a lower surface of the n-clad layer may exist in an n-contact layer between the sapphire substrate and n-clad layer, and a portion of the leaked light may further leak out of the laser device through a cross-sectional end of the substrate and the n-contact layer that is the end of the laser device from which the laser beam emerges. Also, in nitride semiconductor laser devices grown on a GaN substrate, light leaked from a lower surface of the n clad-layer may exist inside the substrate, and a portion of the leaked light may further leak out of the laser device through a cross-sectional end of the substrate that is the end of the laser device from which the laser beam emerges. The leaked light may interfere with a far-field pattern of the laser beam emerging from the semiconductor laser devices, illustrated by the formation of ripples in the graphs illustrated in FIGS. 1A and 1B.
The ripples in the far-field pattern may cause problems in applying the blue-purple semiconductor laser device to a system. For example, when using the blue-purple semiconductor laser devices as blue light source of laser displays, the ripples may make display images uneven and thus deteriorate the quality of screen displays. Also, when used as a light source of optical storage media, the ripple shapes may increase noise, and thus, errors in reading signals during information reproduction, which erodes reliability of the optical pickup.
To decrease the ripples in the far-field pattern, light leakage down from the n-clad layer may be blocked. The optical confinement may be improved by increasing the Al composition ratio in the n-clad layer or making the n-clad layer thicker. However, these methods may be limited because compositions including undesirable amounts of aluminum (Al) or undesirably thick n-clad layers may increase the probability of inducing cracks during growth for semiconductor laser devices. Light leakage may also increase for longer wavelengths of light, which is a drawback with respect to applications, e.g., a source for laser displays.
The conventional art discloses a technique which stops light leakage through a substrate by depositing a light shield membrane on the cross-sectional end of the substrate, which is on the end of the laser device through which a laser beam emerges. According to the conventional art, a semiconductor laser device may be attached to a jig which may screen a region where the light shield membrane should not be formed on the light emission face of semiconductor laser device, so that the light shield membrane may then be deposited on appropriate regions of the end of the substrate.
However, the thickness of the region where the light shield membrane should not be formed may be only a few micrometers, making it difficult to manufacture the jig which may screen the region. If the jig screens the cross-sectional end of the substrate, the light shield membrane may not be sufficiently formed and light leakage may not be sufficiently blocked. In addition, micrometer accuracy may be required when attaching the semiconductor laser device to the jig, but maintaining this degree of accuracy may be difficult. Therefore, the probability that light emission capacity may be deteriorated due to the light emission face being damaged during attachment of the jig to the semiconductor laser device may increase.